Frequency Change with Tape Speed

Question

I recorded my own voice in an old tape recorder. When I put the device in fast forward mode my voice turned a little squeaky. I wonder if the fundamental frequency of the voice had changed? Is that possible?

Answer 1

Yes, it is possible. If it is playing faster, that is outputting the analog value that used to be at time $t$ at time $t/a$ with $a \gt 1$, for some constant value $a$, all the frequencies have been multiplied by $a$.